Hydraulic or pneumatic piston-cylinder devices are commonly used in force or lift apparatus. Depending on the application involved, different sizes or working cylinders must be available for different lifts (strokes) as well as for different force (power) effects. To cover all requirements, therefore a wide range of different piston diameters and piston strokes are necessary. The stocking of such components for a diversity of requirements necessitates a large amount of capital. Another disadvantage of pneumatic or hydraulic piston and cylinder devices is that the size of the end face of the piston is determined by the desired force, or by the pressure of the medium. Reduction of the piston area requires increased pressure of the medium to deliver a given force. For high forces, therefore, undesirably large piston areas may be required.
Pressurized devices for force or lift apparatus utilizing inflatable bellows, which may be connected either in parallel (force addition) or in series (lift addition) are known. Such devices are complicated in construction, are expensive, and are liable to damage. They are generally rigid in construction, and single elements cannot be combined at will to form units which take account of the desired conditions in optimal manner.